EP-A-168892 describes an endothermic steam reforming reaction, which is carried out in a fixed bed situated in at least one pipe in which a temperature of between 800 and 950° C. is maintained by routing at least part of the hot product gas from a partial oxidation reaction along the pipe(s). According to this publication the combined partial oxidation and endothermic production of synthesis gas result in a better yield of synthesis gas, an increased H2/CO ratio, a lower usage of oxygen per m3 of synthesis gas product obtained and a lower capital cost of the plant for the production of CO and H2-containing gas mixtures (as compared to partial oxidation).
A reactor and process for performing a steam reforming reaction is described in DE-A-3345088. This publication describes a reactor vessel for performing a steam reforming reaction starting from a natural gas feedstock. The vessel consisted of a tube sheet from which a plurality of tubes filled with a suitable catalyst extended into the vessel. The required heat of reaction is provided by passing the hot effluent of a partial oxidation reaction of natural gas at the exterior of the reactor tubes in the vessel. Such steam reformer reactors are also referred to as so-called convective steam reformer (CSR) reactors.
U.S. Pat. No. 6,224,789 discloses a process wherein synthesis gas is prepared in a combination of an autothermal steam reforming step and a convective steam reforming step.
WO-A-8801983 discloses a convective steam reforming reactor vessel wherein the hot gas, which is used to heat the reactor tubes, is obtained by burning heating gas in a lower part of the vessel.
The synthesis gas as obtained in the above processes may be used as feedstock in a Fischer-Tropsch process. In typical Fischer-Tropsch processes hydroprocessing steps are performed to covert the Fischer-Tropsch synthesis paraffinic product into valuable products as detergent feedstock, solvents, naphtha, kerosene, gas oil, lubricating base oils and waxes having varying congealing points. Typical hydroprocessing steps are hydrogenation, hydroisomerization, hydrocracking and catalytic dewaxing. For these steps hydrogen is needed. It would be useful to provide an efficient process to simultaneously prepare hydrogen and synthesis gas.